1. Field of the Invention
This invention relates generally to the field of x-ray systems, and more particularly to an x-ray receiver for medical and dental applications that is mountable within an x-ray tube housing.
2. Related Art
X-ray receptors have long been employed in the fields of medicine and dentistry to capture images representing the human anatomy. These images are often used by physicians and dentists to aid in the diagnosis and treatment of conditions and disease. In the case of dentists and oral surgeons, images of a patient's teeth, mouth, and gums are used to aid in diagnosis and treatment. The most conventional technique is to use radiographic film as the imaging receptor. However, solid-state sensors which convert x-rays into an electrical signal have increasingly begun to be used in place of photographic film.
Such filmless radiography systems offer many advantages over traditional film-based radiography. For example, an electronic sensor is typically more sensitive to x-rays than is film, thereby allowing the dosage of x-rays to the patient to be lowered quite significantly. Also, the image of the anatomy may be generated by the computer almost instantaneously, thus improving workflow and eliminating the entire film development process, including the use of potentially harmful chemicals. In addition, because the images are generated electronically, they can be easily stored in and accessed from a computer database.
In digital radiology, the signal from the electronic sensor is typically transmitted to a computer or other output device via a flexible cable. In other systems, however, a wireless interface may be substituted for the cable, such that signals are transmitted from the sensor to the output device via a radio-frequency waveform. Wireless communications systems have made inroads into many disciplines and may be preferable in medical and dental digital imaging for a number of reasons. For example, extra wires can be annoying to the patient and clinician. In addition, in certain diagnostic procedures, the sensor wires may be cumbersome and could limit placement of the sensor with respect to the x-ray tube and computer. In digital dental radiography, such wires can limit sensor placement in the mouth. Furthermore, mechanical failure of the wire due to strain is a common failure mechanism. A wire may also create a trip hazard.
In visible digital imaging, such as conventional digital photographic, the detector is typically integral to the camera housing, which might further include, among other things, a lens and image processing components, and in most cases a flash to augment the ambient light. Designing a camera in such a manner is relatively simple: ambient light and/or light provided by the flash reflects naturally off the subject and towards the detector housed in the camera.
In digital x-ray imaging, on the other hand, the energy source (e.g., the x-ray generator) is typically configured to provide the radiation directly towards the image detector, which is often distant from the source and/or from computer processing components. Thus, as discussed above, the image data is often conveyed from the detector using a long flexible cable, and in certain applications this cable can be inconvenient for the patient and the operator as it may present various electrical and mechanical constraints. A wireless system, on the other hand, can provide a wider range of degrees of freedom of the detector with respect to the source.
More particularly, in digital x-ray imaging, an x-ray beam is projected from an energy source towards an electronic sensor (in filmless dental radiography, for example, the electronic sensor is placed in the patient's mouth behind the tooth to be examined, and the x-ray beam is projected through the patient's tooth). The x-rays impinge on the electronic sensor, which converts the x-rays into an electrical signal. The electrical signal is typically transmitted over a wire to a computer as described above, and the computer then processes the signal to produce an image on an associated output device, such as a monitor or a printer. Alternatively, the electrical signal could be transmitted wirelessly from the electronic sensor to a receiver which in turn delivers the signal to the computer. The electronic sensor may include a charge-coupled device (CCD), an active pixel sensor (APS) array, or another type of filmless radiation sensor.
Examples of filmless radiography systems in the dental field include those described in U.S. Pat. No. 4,160,997 to Schwartz and U.S. Pat. No. 5,434,418 to Schick. An example of a wireless medical x-ray imaging system is provided by U.S. Patent Application Publication 2002/0150214 (Spahn). Spahn discusses a system in which a control unit communicates wirelessly with a detector. Spahn shows the receiver with which the detector communicates housed in a mobile central control device. While Spahn's design may offer some measure of flexibility, it suffers from a number of drawbacks in that it does not address certain technically challenging aspects of achieving its end. In practice, the distance from the transmitter to the receiver must typically be quite limited. This is because the waveform usually carries large volumes of data and may be blocked by obstructions such as medical equipment or the patient's anatomy. In yet other scenarios, such as in intra-oral dental imaging, there may be a limited amount of space available for the transmission circuitry within the sensor, and thus a less stable and lower power voltage controlled oscillator may be used. The overall power available to transmit a pulse may also be limited. And Federal regulatory bodies and hospitals commonly limit the amount of transmitted power that a design may utilize. Thus, the distance between the transmitter and receiver must typically be relatively short.
Moreover, it is often difficult to find a convenient and workable location for the receiver. Medical and dental offices typically contain furniture, equipment, and cabling that together limit the practical location for such a device. In dentistry, for example, an operating room might contain a dental chair, overhead lamps, instruments, trays and drills. Given factors such as these, finding an appropriate location for the receiver and its related circuitry is a formidable task.
Although prior art techniques are generally good for their intended purposes, they do not sufficiently address problems including those explained above. There exists, therefore, a need for finding a location for the receiver and its related circuitry which ameliorates the above-mentioned problems caused by, for example, practical factors such as the limited distance from the transmitter to the receiver, the limited space available for the transmission circuitry within the sensor, and the limited power requirements.